This invention relates in general to rigid metal plates adapted for attachment to bones (typically referred to as bone plates) with screw-type fasteners (typically referred to as bone screws) and to guide devices used to properly align a drill to create the bore in the bone that will receive the screw-type fastener inserted through an aperture in the bone plate. The invention also relates to tubular drill guides that are used to properly align a drill bit when a pilot hole is being drilled into the bone.
With many bone fractures or surgical osteotomies it is necessary to secure the bone segments in a fixed, rigid manner such that natural healing may occur. A common way to accomplish this is to provide a rigid metal plate shaped and sized as required to correspond to the bone or bones being secured, the rigid plate having apertures to receive bone screws, the bone screws being inserted through the plate and into the bone to secure the plate to bone and thereby prevent relative movement of the bone segments during the healing process. Additionally, bone plates are utilized in distraction procedures—the bone plates being affixed to opposing bone segments that are slowly separated by a distraction mechanism in known manner to lengthen the bone by osteogenesis. In most cases it is desirable or even necessary to first drill a pilot hole or bore into the bone at the location for each screw so as to prevent fracturing or splintering of the bone when the bone screw is inserted. Given the need to reduce undesirable stresses within the bone material and to accurately and securely attach the bone plate to the bone, it is important that the bores are properly aligned relative to the bone plate and screw receiving apertures, especially when the screw receiving apertures are beveled, shouldered, threaded or otherwise configured to better mate or correspond to a particular bone screw configuration.
While the pilot holes may be drilled by first marking the location of the screw receiving apertures on the bone through the screw-receiving apertures, removing the bone plate and then manually aligning the drill bit with the markings, a better known methodology for creating the screw-receiving pilot holes is to utilize elongated, tubular drill guides that are aligned with the screw receiving apertures. The drill guides may be temporarily attached or mounted to the bone plates to extend proximally from the screw receiving apertures in order to insure proper location and alignment of the pilot hole and bone screw relative to the bone plate. With such an assembly, the bone plate is manually held or temporarily affixed in proper position over the bone or bone segments, the drill bit is inserted into the drill guide so as to extend through the screw receiving aperture to the bone, the pilot hole is created in the bone, the bit is removed from the drill guide, the drill guide is detached from the bone plate, and the bone screw is inserted through the screw receiving aperture and into the pilot hole to secure the bone plate to the bone.
A problem that has been noted with the known systems is that the removal of the drill guide members from the bone plate prior to insertion of the bone screws into the apertures often results in movement of the bone plate relative to the bone or bone segments and the pilot holes that have been created. This may result in misalignment of the bone screws when they are implanted to secure the bone plate to the bone or misplacement of the bone plate.
It is an object of this invention to address this problem by providing a bone plate locking cannula and drill guide assembly, and its method of use, wherein locking cannulas are temporarily attached to the bone plate in proper alignment with the screw-receiving screw receiving apertures, the cannulas being sized to receive a tubular drill guide. The bone plate, screw receiving apertures, bone screws, drill bits, drill guides and locking cannulas of the assembly are sized and structured such that after drilling the pilot bore into the bone and removing the drill bit and drill guide from the locking cannula, the internal diameter of the locking cannula is sufficiently large such that the bone screw may be inserted through the cannula and driven into the bone through the screw receiving aperture to secure the bone plate to the bone without requiring removal of the locking cannula. After the bones screw is fully inserted into the bone, the locking cannula is then removed from the bone plate. These and other objects not expressly set forth in this section will be supported or made obvious based on the following disclosure.